“This is so far the largest genetic study of the inflammatory bowel diseases (IBD), which include Crohns disease,” says Dr Mauro D’Amato, associate professor at Karolinska Institutet’s Department of Bioscience and Nutrition and leader of the Swedish part of the study. “Based on the new results, we can now explain 23 per cent of the genetic predisposition to Crohn’s disease.”

The study, which is published in the scientific journal Nature Genetics, is based on a genetic survey of over 22,000 Crohn’s disease patients and 29,000 controls from Europe, North America, New Zealand, and Australia. an estimated 25,000-plus people in Sweden have Crohn’s disease, and over 500 new cases are diagnosed every year. Crohns disease is a chronic inflammation of the bowels; it is intermittent and commonly manifests with symptoms such as diarrhoea and abdominal pain, but also fever, rectal bleeding, weight loss, fatigue, joint pain, and skin disorders can be part of the clinical picture. Crohn’s disease is treated with anti-inflammatory drugs and/or surgery.

Earlier twin studies have shown that Crohn’s disease is caused by the interaction of genetic and environmental factors, and people with affected relatives are at higher risk of developing the disease. in the present study, researchers have identified a total of 71 genes associated with Crohn’s disease. in line with previous results, most of these genes are involved in the control of the interactions between the intestinal bacterial flora and local immune cells in the mucosa, and in the activation of what is known as the adaptive immune response.

“The most exciting findings may come now from the identification of the biological role of those genes for which we know very little or nothing at all,” says Dr D’Amato.

The study is one of several projects being conducted within the frame of the International IBD Genetic Consortium (IIBDGC), and has been coordinated by the corresponding author Dr Miles Park from the University of Cambridge. The researchers hope that future large-scale studies will provide clues as to why inflammatory bowel diseases occur. This will ease diagnosis and enable doctors to design improved therapeutic strategies.